Professor Nick Cutter (Douglas Henshall) - A Professor or evolutionary biology and team leader. His wife Helen was 'killed' 3 years before the start of the program. In Series 3 his wife comes to kill him and succeeds with her small army of Cleaner Replicas. He had a strong love interest in Claudia Brown but because he altered time when he went to kill the future predator Jennifer Lewis took her place. Just before his death, Jennifer also starts to have feelings for Cutter.
Stephen Hart - (James Murray) - Acting as Nicks lab technician and body guard. He sacrifices his own life to save that of Cutter and the rest of the team.
Claudia Brown (Lucy Brown) - In the first series, Claudia was the Home Office Offical and acting as a government liaison, but at the end of Episode 6 she disappeared.
Captain Tom Ryan (Mark Wakeling) - Special force leader and S.O.S agent. He is killed off at the end of Series 1.
Oliver Leek (Karl Theobald) - Lester's Assitant and replacement for Claudia Brown. he suddenly appears at the beginning of series 2, and it is soon discovered he is in league with Helen.
Caroline Steel (Naomi Bentley) - One of Connor's Ex-Girlfriend who appears in series 2. She was in league with Leek.
Christina Johnson (Belinda Stewart-Wilson) - Lesters new bosses. Is killed by a future predator.